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We will be holding a virtual Pro-QM Zeminar this week on Wed. 6/21 at 3:30pm ET. Our speaker will be Dr. Tobias Holder from the Weizmann Institute (https://scholar.google.com/citations?user=xfDidrkAAAAJ&hl=en)
Speaker: Tobias Holder
Title: Unique transport signatures in magnetic materials: Connecting semiclassics and quantum perturbation theory at nonlinear order
Abstract: In the last few years, nonlinear responses have become increasingly important for the study and characterization of quantum materials, with the nonlinear anomalous Hall conductivity and the bulk photovoltaic effect being particularly successful examples. At the same time, from a theory perspective nonlinear response is challenging for two reasons: Firstly, the corresponding expressions are often unwieldy, and secondly many of the physical intuitions acquired at linear order seem to fail beyond linear order. Hence, for decades several key aspects of nonlinear transport have remained controversial. In this talk, I will present a new framework which connects the concepts of anomalous motion, coherent interband transitions, and wavepacket deformations. I show in which cases the Green-Kubo formalism can be continued to zero frequency to recover the Boltzmann kinetic approach and discuss two novel phenomena in the nonlinear conductivity: The appearance of a mixed axial-gravitational anomaly in magnetic metals and a nonlinear quantum anomalous Hall effect in certain magnetic insulators. [2208.00827,2209.09531]
The seminar will be held virtually over Zoom:
https://columbiauniversity.zoom.us/j/97171267603?pwd=U2wrVEUrbkhOV0NSOUdOeDZhK2d3Zz09
Meeting ID: 971 7126 7603
Passcode: 897903